Hydriding kinetics and process parameters in reactive milling

We focus on the hydriding kinetics of Mg2Ni/Ni nanocrystalline and Zr55Cu30Al10Ni5 amorphous powders under reactive milling conditions. A methodological approach, based on mechanochemical parameters, is presented to quantify the different behaviour shown by the two systems. A decelerating course characterized the H2 absorption rate in the Mg based powders. Although they were able to absorb H2 under static conditions, a speeding up of the kinetics was observed under milling. The mechanochemical gain, gm, that is the rate increase at the milling outset, was found to depend on the specific milling intensity IM. By contrast an incubation period preceded the absorption in the case of the Zr based amorphous powders. Furthermore, S-shaped trends described the reactive behaviour in this case even if the kinetics was still dependent on IM. Irrespective of the milling intensity it was found that the same mechanical work, that is the energy dose, was required to reach the maximum hydriding rate.